Bring the documentation in line with the implementation across public-header
docstrings and the Antora manual.

Headers:
- read_until: the match position is returned on success, not on error.
- dynamic_buffer: flat/circular/vector/string are all adapters over external
  storage; the value-type category is for user-defined owning buffers.
- Add missing docstrings to public symbols: task/quitter promise types, the
  delay awaitable, fuse::result, make_buffer overloads, the recycling memory
  resource, and frame_alloc_mixin's operator new.
- Remove buffer_param references to a nonexistent max_size member.
- Note that the recycling memory resource ignores the requested alignment.
- Fix this_coro/run_async examples and document the environment precondition.
- Correct the executor concept example, io_runnable handle() constness, the
  executor_ref example, pull_from parameter descriptions, and timeout/when_all
  and when_any @throws clauses.
- Name strand's template parameter Ex and correct its dispatch condition.
- Correct the overstated no-throw guarantee on the test mock streams.

Manual:
- IoAwaitable: the custom-awaitable example resumes the caller by wrapping its
  handle in a continuation and posting that to the executor; dispatch/post take
  a continuation&, not a raw coroutine_handle.
- Construct buffers from arrays/containers with make_buffer, not mutable_buffer
  (which has no array/range constructor), in the read/stream examples; a
  string_view is not itself a ConstBufferSequence and must be wrapped with
  make_buffer.
- Document the real fixed 16-entry buffer window for system I/O.
- Correct the mock source/sink prose and member tables.
- async_event is a manual-reset event, not one-shot.
- Fix the custom-dynamic-buffer read loop to check end-of-stream before commit.
- Remove a misplaced whole-catalog summary section.
- Correct the type-erasure vtable taxonomy and the run_async wrapper snippet.
- Replace the cancellation page's timeout example with the real timeout()
  combinator; bind executor_ref to a named executor.
- Document when_all/when_any all-fail semantics (when_any reports an unspecified
  failure); replace the FrameAllocator concept with the real allocator
  requirements and document frame_alloc_mixin.
- Document read into a DynamicBuffer, the ReadSource read overload, read_until,
  and write_now; the composed write takes its buffer sequence by value.
- Smaller buffer/stream/source corrections (byte-size note, empty/partial read).

Buffer and stream specification:
- Explain that const_buffer/mutable_buffer are non-owning handles: the caller
  owns the underlying bytes and their lifetime; the library manages only the
  handles and handle-sequences it produces.
- Strengthen the rationale for void* over std::byte/span, and state that
  treating a single buffer as a one-element sequence is a deliberate
  convenience applied consistently across the buffer API.
- Note on the ReadStream/WriteStream concepts that the single buffer archetype
  in the requires-clause is only a representative: the real contract is that
  the operation accepts any MutableBufferSequence / ConstBufferSequence, which
  a C++ concept cannot fully express.

Addresses cppalliance#273, cppalliance#287, and cppalliance#296.